Hey Fly I also put 75 in 1 acre pond 3 years ago. I now catch about 3 or 4 a year maybe on a hook with worms. I would bet that some of them are still there. My dad caught a real nice one last year it was about 7.5 inches. It hit on a mini hula popper believe it or not. Here is the pic.
The only difference between a rut and a Grave is the depth. So get up get out of that rut and get moving!! Time to work!!